Add option to disable following symlinks

[adriansr]

Which operating system (GOOS) and version are you using?

GOOS: darwin
ProductName: Mac OS X
ProductVersion: 10.12.6
BuildVersion: 16G1036

Please describe the issue that occurred.

Under macOS, fsnotify follows symlinks on watched directories and produces notifications for changes to files residing on directories pointed by the symlink.

Are you able to reproduce the issue? Please provide steps to reproduce and a code sample if possible.

1. The usual watcher / logger:

package main

import (
	"log"

	"github.com/fsnotify/fsnotify"
)

func main() {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		log.Fatal(err)
	}
	defer watcher.Close()
	err = watcher.Add("/tmp/bug")
	if err != nil {
		log.Fatal(err)
	}
	for {
		select {
		case ev := <-watcher.Events:
			log.Printf("Got event %+v", ev)
		}
	}
}

Operations to perform:

mkdir /tmp/bug
mkdir /tmp/other
ln -s /tmp/other /tmp/bug/link
touch /tmp/other/somefile

Events received:

2017/12/11 23:44:38 Got event "/tmp/bug/link": CREATE
2017/12/11 23:44:41 Got event "/private/tmp/other/somefile": CREATE

[bep]

And this is wrong? Why?

[adriansr]

@bep I understand the watching is meant not to be recursive?

If instead of linking to another directory, I just create the directory inside a watched directory, I don't get notifications for it. Why would I want symlinks to behave differently?

Also, this behavior is only displayed in macOS. Not Linux or Windows.

[nathany]

see #199 and #289.